Hydroponics is the science of growing plants using nutrient solutions in water to replace traditional soil. It has long been know that plants absorb essential nutrients through inorganic ionic transfer that occurs through a soil substrate. However, the soil merely acts as a storage medium for the necessary nutrients and as a physical support structure for the plant roots. The soil itself is not the necessary component for plant growth. Almost any plant can be grown in an aqueous solution if the plant is physically supported and minerals essential to the plant's growth are introduced into the system.
In hydroponic growing systems, there is a wide array of substrates available for supporting the plant root structure. Such substrates include clay aggregates, glass beads, rice hulls, perlite, pumice, vermiculite, sand, gravel, and many others. The plant nutrients in a hydroponic system are dissolved in the water and delivered to the plants in ionic form as both cations and anions. The essential ionic nutrients for plant growth include calcium, magnesium, potassium, nitrates, nitrites, sulfates, and phosphates. Hydroponics has long been the preferred method of growing plants in scientific and research environments, where nutrient levels, light, and other environmental factors can be more easily and accurately controlled.
The advantages of hydroponic systems are numerous. Significantly, hydroponic systems can be used to grow plants in areas where the soil is either non-existent or insufficient to sustain plant growth. For example, in the 1930's hydroponic grow beds were used by the PanAm airline company to grow beans, tomatoes, and other vegetables for passengers and crew to eat during refueling stops on Wake Island in the middle of the Pacific Ocean. Also, the amount of water needed to grow plants in a hydroponic system is significantly less than traditional irrigation methodology because the water is recycled through the system. Further, hydroponics offers stable and high plant yields, ease of harvesting, and less nutrition pollution because the system is a closed loop. The disadvantages to hydroponics include high costs associated with the grow systems and the expense and difficulty of artificial nutrient delivery.
In the 1970's, researchers and hobbyists began to introduce fish into the aquatics of a hydroponic system. The inclusion of fish or any other aquatic species into a closed hydroponic loop became known as aquaponics. In an aquaponic system, the aquatic species, usually fish, produce the nutrient laden materials, namely ammonia, nitrites and nitrates, that are beneficial to improved plant production. The plants, in turn, clean the water of the fish waste while also adding oxygen back into the system. A single aquaponic system with both plants and fish offers a more robust and efficient method for producing not only healthy plants with higher crop yields but also healthy fish, which can also be a nutrient source for human consumption. The advantages of an aquaponic system over a pure hydroponic system is that the former produces both fish and plants while reducing the amount of artificial nutrients introduced into the system. Aquaponic systems are seen as a more natural and harmonious method of both plant and fish production.
Most aquaponic systems utilize a grow bed with a bell siphon for periodic recycling of the plant water into the fish tank and a pump for continuously moving the water from the fish tank into the grow bed. The water is removed from the grow bed to introduce oxygen to the roots of the plants. In the prior art, the bell siphon is placed either in the center or on the inside edge of the grow bed. For example, U.S. Pat. App. No. 2013/0047508 A1 discloses a single-bed system with the bell siphon (240) located in the back right corner of the bed. Another example is U.S. Pat. App. No. US 2014/0041594 A1, where the bell siphon (38) is shown in FIGS. 1 and 2 to be located in the middle of the grow bed. One disadvantage of locating the bell siphon in the grow bed is that the bell siphon takes up space that would otherwise be used for growing plants. Another disadvantage of this location is that the plant roots tend to grow down into the feed holes located at the bottom of the bell siphon, clogging the bell siphon and reducing the system efficiency.
An aquaponic system with a single grow bed is fairly simple to tune. The periodic discharge of plant water into the fish tank and the continuous recycle of the fish water into the single grow bed is straightforward and both the plants and the fish adapt quickly to the cycle. Introducing multiple grow beds into the system, however, poses numerous challenges that have not been resolved in the art. Multiple grow beds discharging into the same fish tank stress the fish; multiple grow beds with multiple bell siphons tend to fall out of sync and lead to uncontrolled charging and discharging of the tank and the beds thereby threatening to flood the facility and damage equipment and other system resources; and multiple grow beds complicate the water management of the overall system.
There exists a need in the art for a controlled aquaponic system that provides predictable flood, drain, and fluid delivery to both plants and fish. There further exists a need in the art for an aquaponic system that can selective control effluent release from grow beds to more quickly harmonize the overall system. There further exists a need in the art for a controlled aquaponic system that is more reliable and robust.